Turbine



jatented Mar. 15, 1927.

UNITED STATES 1,620,663 VPATENT OFFICE.

ALEXANDER T. KASLEY, OF ESSINGTON, PENNSYLVANIA, ASSIGNOR TO WESTIN G- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

Y TURBINE.

Application filed April 12, 1923. Serial No. 631,672.

My invention relates to turbines, more particularly to those of the marine type, and it has for its object to provide apparatus ofthe character designated which shall have means to oppose the pumping action of ahead blading and possible consequent breakage thereof when the reversing blading is in operation.

Trouble has been encountered on account of the breakage of ahead marine turbine blading of the reaction type, particularly when rotating idly with the astern blading in operation. Since breakage has `occurred safely within the allowable centrifugal stresses of the ahead blading, such breakage is apparently due to induced vibrations of fluid set up in the ahead blading incident to astern operation. This is further shown by the fact that breakage has occurred from `the last row of reaction blading well back toward the high-pressure end and including some of the 4shorter blading.

It is well known that, if reaction blading is operated backwards, it develops a pumping action or acts as a compressor. With the inlet end of ahead blading of this type closed, reverse operation thereof results in the development ofliuctuating pressures or pressure Waves whose frequency is dependent upon the turbine speed. If these pressure waves or fluid vibrations or some higher harmonics thereof are resonant with the natural period of any of the blading, then a condition of resonance may take place, rcsulting in excessive amplitudes of vibration of such blading and possible breakage thereof. The natural frequency of the reaction blades increases as they become shorter. Hence, when the astern or reversing section is operated, pressure waves or fluid vibrations, due to the pumping action of the ahead reaction blading and having a frequency dependent upon the speed, change in frequency as the speed increases; and, when the fluid vibrations or pressure waves or their harmonics are resonant with the natural period of any of the blades, dangerous vibrations of the latter may be set up. As the reversing speed is changed, resonance may occur with successive rows of shorter blading, thereby explaining the breakage 0f reaction blading of a large part of the turbine as already referred to.

Accordingly, it is the object of my invention to provide means to supply steam to the inlet end of the ahead blading, Whenever the astern blading is in operation, to secure such a speed of flow as to minimize or eliminate the development of pressure Waves of fluid and consequent resonant vibration of the blading and breakage of the latter.

Appaartus made in accordance with my invention is illustrated in the accompanying drawings, forming a part of this application, in which Fig. l is a diagrammatic view showing a marine turbine installation with my improvement applied thereto; and Fig. 2 isa detail view showing valves in section used in Fig. l.

- Referring now to the drawings for a better understanding of my invention, in Fig. l, I show a turbine having an ahead section 30, and a reversing or astern section3l. Steam is supplied to the ahead section 30 by any suitable conduit or passage 32, including a valve 34.` In like manner steam is supplied to the reversing section 31 by a conduit 33 having a valve 35.

With the structure described, when the reversing section 3l is in operation the reac- 8o tion blading 37 of the ahead section 30 develops a pumping action and consequent pressure waves or vibrations in the fluid. As already pointed out, if such pressure waves should be resonant with the natural period of any of the blades, dangerous vibrations and possibly breakage of the latter might occur. I therefore provide means, in connection with an arrangement of this character, which shall assure opposition to the development of pressure Waves whenever the reversing section is in operation.

The means referred to comprises a conduit 36 connected to the inlet of the reversing section 3l, and to the inlet of the ahead 95 section 30. This conduit or passage includes a check valve 2S which opens in the direction of the inlet of the ahead section 30, and closes in the other direction. The check valve therefore serves to prevent by-passing of any of the steam from the ahead section when the latter is in operation. However, when the reversing section 31 is in operation, some of the steam passing through the valve 35 passes through the conduit 36 and 105 enters at the inlet end of the ahead section 30, passing through the reaction blading 37 of said section. The pressure of steam passing through the conduit 36 and the volume thereof are sufficient to develop a counterow throughtheahead section. which shall effectively oppose a pumping action` and consequent pressure of Waves and resonant vibration oi' the reaction blading 37.

It is desirableV that the minimum quantity orV steam shall be used' for the purpose of opposing the pumping action.

which may be permanently setto sup ly just enough steam tor the purpose stated). The direction of flow through thevconduit 27 to minimize pumping effects ot the reaction blading isindicated by the arrows in Fig. l. An example ot check` and throttle valves Suitable tor my purpose Vmore clearly appear in Fig- 2;

F rom the foregoing description, the operationl ot apparatus made in accordance With my invention will be obvious.. Steam .is supplied from any suitable source to the ahead reaction hlading in order to; oppose the pumping action and consequent resonant vibration ot such lading Vwhenever the astern section is in operation.

Vhile I have shown my invention in but two` forms, it Willbe obvious tothose skilled inthe art that itis not soli'mited, but is susceptible-,ot various other changes and modi.- cations Without departing tromA the spirit thereof, and I desire,theretore, that only suehlimitations shall be placed thereupon as are,` imposed by the prior art or as` are speciiically set Jorth in the appended claims.

I, therefore,` show a throttle valve 29 in the conduit 27" WhatI claim is: v v

l. In a, turbine installation, anA ahead section which develops a pumping action when operating reversely,A a reversing section, a conduit between the inlet ends of" said sections, anda check valve in the conduit which opens in the direction of the inletende of the ahead section, whereby, When the reversing section isin operation, steam is also supplied to the inlet end of the ahead section.

2. In a turbine installatiorn, an ahead vsection including reaction blading, a. reversing section, a conduit between the` inlet ends ot' said. sections, and` a check valve. in. the conduit opening in the direction ot theinlet end of the ahead section, whereby, when the, reversing section is in operation, steam is sup.- plied to the inlet end of thereaction blading ot the ahead section.. Y

3. In a turbine installation, aan ahead section including reaction blading, a reversing section,l a conduitV between the inlet ends` of said sections, a check valve in the conduit opening in the; direction of they inlet end of the ahead section,y whereby, When` the reversi-ng sectionis in` operation, steamis supplied` to the inletend ot the reaction blasting, and` an adjustable throttle valve.y thel conduit :tor regulating the rate of flow there.- through.A

In testimony Whereot, I'have liereuntosub. scribed my name this 9th day of Aprill923..

v ALEXANDER T'.. KSLEY. 

